Sheet metal turbine housing with biaxial volute configuration

ABSTRACT

Turbine housing assemblies and related turbocharger systems are provided. One exemplary turbine housing assembly includes and inner shell and an outer shell. The inner shell includes an inner base portion defining an inlet and a volute portion defining an outer contour of a volute in fluid communication with the inlet. The outer shell circumscribing the volute portion in a radial plane and includes an outer base portion circumscribing the inner base portion. The inner shell includes a first plurality of sheet metal structures joined to one another in the radial plane, the outer shell includes a second plurality of sheet metal structures, and first portions of the second plurality of sheet metal structures surrounding the volute portion are joined to one another in an axial plane transverse to the radial plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter described here is related to the subject matterdescribed in U.S. patent application Ser. No. 15/419,320, U.S. patentapplication Ser. No. 15/419,429, and U.S. patent application Ser. No.15/419,472, all filed concurrently herewith.

TECHNICAL FIELD

The subject matter described herein relates generally to flow controlsystems, and more particularly, to turbine housings for use inturbocharger systems.

BACKGROUND

Turbocharger systems are frequently used to improve the efficiency ofinternal combustion engines. Two-stage turbocharger systems can be usedto further improve the engine efficiency over a single-stageturbocharger system including a single turbine and a single compressor.While use of two-stage turbocharger systems may be desirable inautomotive vehicles, for example, to achieve fuel economy targets orother environmental goals, the combination of the added financial costin conjunction with the size, packaging, assembly, or installationconstraints may be prohibitive. Additionally, introducing turbines intothe exhaust gas flow can reduce the temperature of the exhaust gas andmay reduce the effectiveness of downstream emissions control devices,such as a catalytic converter. Accordingly, it is desirable to provide aturbine housing having lower thermal inertia while also achieving otherperformance objectives and maintaining structural integrity.

BRIEF SUMMARY

Turbine assemblies and related turbocharger systems having directturbine interfaces are provided. An exemplary turbine assembly includesa bypass valve assembly structure including a guide portion, an innersheet metal shell including an inner inlet portion and a volute portionproviding an outer contour of a volute, wherein an end of the innerinlet portion is surrounded by the guide portion and spaced apart fromthe bypass valve assembly structure, and an outer sheet metal shellradially surrounding at least a portion of the volute portion andincluding an outer inlet portion surrounding the inner inlet portion andcontacting the guide portion of the bypass valve assembly.

In another embodiment, turbine housing assembly includes a cast metalstructure having an inlet opening and a bypass opening transverse to theinlet opening, an inner sheet metal shell including an inner baseportion having an end disposed within the inlet opening and a voluteportion that defines an outer contour of a volute, and an outer sheetmetal shell that surrounds the volute portion and includes an outer baseportion that circumscribes the inner base portion, wherein the outerbase portion is joined to the cast metal structure and the end of theinner base portion is freestanding with respect to the cast metalstructure.

In yet another embodiment, a turbine housing assembly includes a castbypass valve assembly structure including a guide portion about an inletopening and a bypass opening transverse to the inlet opening, an innersheet metal shell including an inner inlet portion and a volute portionthat defines an outer contour of a volute, wherein an end of the innerinlet portion is disposed within the inlet opening and surrounded by theguide portion, and an outer sheet metal shell that surrounds the voluteportion and includes an outer inlet portion circumscribing the innerinlet portion and contacting the guide portion of the bypass valveassembly, wherein the outer inlet portion is joined to the cast bypassvalve assembly structure and the end of the inner inlet portion isfreestanding with respect to the cast bypass valve assembly structure.

Another embodiment of a turbine housing assembly includes an inner shellhaving an inner base portion defining an inlet and a volute portiondefining an outer contour of a volute in fluid communication with theinlet. The turbine housing assembly also includes an outer shellcircumscribing the volute portion in a radial plane and including anouter base portion circumscribing the inner base portion, wherein theinner shell comprises a first plurality of sheet metal structures joinedto one another in the radial plane, the outer shell comprises a secondplurality of sheet metal structures, and first portions of the secondplurality of sheet metal structures surrounding the volute portion arejoined to one another in an axial plane transverse to the radial plane.

In another embodiment, a turbine housing assembly includes an innershell comprising a first plurality of sheet metal structures joined toone another at a first seam in a radial plane and an outer shellcomprising a second plurality of sheet metal structures joined to oneanother at a second seam in an axial plane transverse to the radialplane. The inner shell includes a volute portion defining an outercontour of a volute in the radial plane, the outer shell substantiallysurrounds the volute portion and encloses the volute portion in an axialdirection, and an outer base portion of the outer shell circumscribes aninner base portion of the inner shell that defines an inlet in fluidcommunication with the volute.

In yet another embodiment, a turbine housing assembly includes an innersheet metal shell comprising a first pair of sheet metal structurescoupled together along a radial plane orthogonal to a turbine wheelrotational axis and an outer sheet shell comprising a second pair ofsheet metal structures coupled together along a first plane transverseto the radial plane. Each of the first pair of sheet metal structuresincludes a volute portion defining an outer contour of a volute in theradial plane and a base portion defining an inlet in fluid communicationwith the volute, and each of the second pair of sheet metal structuresincludes an arcuate portion radially overlapping at least a portion ofthe volute portions in the radial plane and an outer base portionradially overlapping at least a portion of the base portions in a secondplane transverse to the radial plane.

Another embodiment of a turbine housing assembly includes an inner shelldefining an inner inlet portion and a volute portion providing an outercontour of a volute, the inner shell comprising a first plurality ofsheet metal structures coupled together in a first plane, an outer shellsurrounding the volute portion and defining an outer inlet portioncircumscribing the inner inlet portion, the outer shell comprising asecond plurality of sheet metal structures coupled together in a secondplane transverse to the first plane, and one or more energy absorbingmembers coupled to an inner surface of the outer shell between the outershell and the inner shell.

In another embodiment, a turbine housing assembly includes an innershell comprising a first pair of sheet metal structures joined to oneanother at a first joint in a radial plane, an outer shell comprising asecond pair of sheet metal structures joined to one another about theinner shell at a second joint in an axial plane transverse to the radialplane, the second pair of sheet metal surfaces each having an innersurface, and a pair of energy absorbing members on a respective one ofthe inner surfaces of the second pair of sheet metal structures, whereinthe pair of energy absorbing members are disposed proximate an interfacebetween the second pair of sheet metal structures.

In yet another embodiment, a turbine housing assembly includes a thinnerinner sheet metal shell comprising a first pair of sheet metalstructures interfacing and joined to one another in a radial planeorthogonal to a turbine wheel rotational axis, and a thicker outer sheetshell comprising a second pair of sheet metal structures interfacing andjoined to one another in a first plane transverse to the radial plane,and a third pair of arcuate sheet metal structures, wherein each of thefirst pair of sheet metal structures includes a volute portion definingan outer contour of a volute in the radial plane and a base portiondefining an inlet in fluid communication with the volute, each of thesecond pair of sheet metal structures includes an arcuate portionradially overlapping at least a portion of the volute portions in theradial plane and an outer base portion radially overlapping at least aportion of the base portions in a second plane transverse to the radialplane, and each of the arcuate sheet metal structures is disposedbetween the volute portions of the first pair of sheet metal structuresand the arcuate portion of a respective sheet metal structure of thesecond pair of sheet metal structures.

Another embodiment of a turbine housing assembly includes a corestructure having a voided inner region defining an axial outlet and anouter surface defining an inner contour of a volute, an inner sheetmetal shell comprising an inner base portion defining an inlet in fluidcommunication with the volute and a volute portion defining an outercontour of the volute, wherein at least a portion of the core structuredefining the axial outlet extends in an axial direction through anopening in the inner sheet metal shell defined by the volute portion,and an outer sheet metal shell surrounding the volute portion andincluding an outer base portion circumscribing the inner base portion.

In another embodiment, a turbine housing assembly includes an innersheet metal shell comprising a first pair of sheet metal structuresjoined to one another in a radial plane orthogonal to a turbine wheelrotational axis, wherein each of the first pair of sheet metalstructures includes a volute portion defining an outer contour of avolute in the radial plane and an opening for an axial outlet and a baseportion defining an inlet in fluid communication with the volute. Theturbine housing assembly also includes a core structure disposed withinthe opening, the core structure having a voided inner region definingthe axial outlet and an outer surface defining an inner contour of thevolute, and an outer sheet metal shell comprising a second pair of sheetmetal structures joined to one another about the inner sheet metal shellin a first plane transverse to the radial plane.

In yet another embodiment, a turbine housing assembly includes a castbypass valve assembly structure including a guide portion about an inletopening and a bypass opening oblique to the inlet opening, an innersheet metal shell including an inner inlet portion and a volute portiondefining an outer contour of a volute, wherein an end of the inner inletportion is disposed within the inlet opening and received by the guideportion, a cast core structure disposed within an opening defined by thevolute portion of the inner sheet metal shell, the core structure havinga surface defining an inner contour of the volute, and an outer sheetmetal shell surrounding the volute portion and including an outer inletportion circumscribing the inner inlet portion and contacting the guideportion of the bypass valve assembly structure, wherein the outer inletportion is joined to the cast bypass valve assembly structure and theend of the inner inlet portion is freestanding with respect to the castbypass valve assembly structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the subject matter will hereinafter be described inconjunction with the following drawing figures, wherein like numeralsdenote like elements, and:

FIG. 1 is a schematic illustration of a two-stage turbocharger system inone or more exemplary embodiments;

FIG. 2 is a perspective view of an exemplary turbine housing assemblysuitable for use in the two-stage turbocharger system of FIG. 1 in oneor more exemplary embodiments;

FIGS. 3-4 are plan views of the turbine housing assembly of FIG. 2;

FIG. 5 is an exploded perspective view of the turbine arrangement ofFIGS. 2-4;

FIG. 6 is a cross-sectional view of the turbine arrangement of FIGS.2-5, taken along line 6-6 in FIG. 3;

FIG. 7 is a partial cross-sectional view of the turbine arrangement ofFIG. 6 taken along the line 7-7 in FIG. 6; and

FIG. 8 depicts a top view of the bypass valve assembly structure in theturbine arrangement of FIGS. 2-6 in accordance with one or moreexemplary embodiments; and

FIG. 9 is an enlarged cross-sectional view of a portion of the turbinearrangement of FIG. 6 in accordance with one or more embodiments.

DETAILED DESCRIPTION

Embodiments of the subject matter described herein relate toturbocharger systems that include one or more turbine stages having amultilayer sheet metal housing. As described in greater detail below inthe context of FIGS. 2-8, in exemplary embodiments described herein, theturbine housing includes an inner sheet metal shell that defines atleast a portion of the volute for a turbine wheel and an outer sheetmetal shell that radially encloses the inner sheet metal shell whilealso enclosing the inner sheet metal shell in the axial directionopposite the turbine wheel. It should be noted that many alternative oradditional functional relationships or physical connections may bepresent in an embodiment of the present disclosure. In addition, whilethe figures shown herein depict an example with certain arrangements ofelements, additional intervening elements, devices, features, orcomponents may be present in an actual embodiment. It should also beunderstood that the drawings are merely illustrative and may not bedrawn to scale.

As used herein, the term “axial” refers to a direction that is generallyparallel to or coincident with an axis of rotation, axis of symmetry, orcenterline of a component or components. For example, in a cylinder ordisc with a centerline and generally circular ends or opposing faces,the “axial” direction may refer to the direction that generally extendsin parallel to the centerline between the opposite ends or faces. Incertain instances, the term “axial” may be utilized with respect tocomponents that are not cylindrical (or otherwise radially symmetric).For example, the “axial” direction for a rectangular housing containinga rotating shaft may be viewed as a direction that is generally parallelto or coincident with the rotational axis of the shaft. Furthermore, theterm “radially” as used herein may refer to a direction or arelationship of components with respect to a line extending outward froma shared centerline, axis, or similar reference, for example in a planeof a cylinder or disc that is perpendicular to the centerline or axis.In certain instances, components may be viewed as “radially” alignedeven though one or both of the components may not be cylindrical (orotherwise radially symmetric). Furthermore, the terms “axial” and“radial” (and any derivatives) may encompass directional relationshipsthat are other than precisely aligned with (e.g., oblique to) the trueaxial and radial dimensions, provided the relationship is predominatelyin the respective nominal axial or radial direction.

As described in greater detail below, the inner sheet metal shellincludes a pair of sheet metal structures that face one another in theaxial direction and are substantially circumferentially joined to oneanother in a radial plane to define the outer portion of the volute. Theinner sheet metal shell includes a central opening for receiving a corestructure that defines an axial outlet for the turbine. The corestructure includes an inner voided region that receives and supports anose of a turbine wheel that rotates in the radial plane within acentral region that is radially circumscribed by the volute. At least aportion of the outer surface of the core structure faces an innersurface of the inner sheet metal shell and is contoured to define theinner portion of the volute opposite the outer portion of the volutedefined by the contoured inner surface of the inner sheet metal shell.In other words, the core structure and the inner sheet metal shellcooperatively define the volute for the turbine that radially surroundsthe turbine wheel.

The outer sheet metal shell includes a second pair of sheet metalstructures that face one another in a direction aligned with the radialplane and are joined in an axial plane that is transverse to orotherwise intersects the radial plane in which the inner sheet metalshell is joined. In this regard, the inner and outer sheet metal shellsprovide a biaxial housing configuration for the volute of the turbine.In exemplary embodiments, the inner sheet metal structures arerelatively thin to reduce the thermal inertia associated with theexhaust gas passageway while the outer sheet metal structures arethicker to provide added containment robustness. In some embodiments,the thickness of the outer sheet metal structure is at least twice thethickness of the inner sheet metal structure. Additionally, in exemplaryembodiments, energy absorbing members (or dampers) are provided on innersurfaces of the outer shell sheet metal structures at locationssusceptible to impact. In one or more embodiments, the total combinedthickness of the inner sheet metal, the outer sheet metal, and theenergy absorbing members is substantially equal to the thickness of acorresponding cast housing structure that would otherwise be utilized inlieu of the sheet metal shells. In some embodiments, the total combinedthickness of the inner sheet metal, the outer sheet metal, and theenergy absorbing members is greater than the thickness of acorresponding cast housing structure to provide equal or greaterrobustness as the cast component. In this regard, the energy absorbingmembers may allow for the thickness of the sheet metal shells at or nearthe inlet and/or the outlet of the turbine housing to have a combinedthickness that is less than the cast component thickness while stillachieving sufficient containment at or around the volute portion of theturbine housing.

In exemplary embodiments, the inlet of the sheet metal turbine housingdefined by the inner and outer sheet metal shells is joined to a bypassvalve assembly, which is realized as a cast metal. As described ingreater detail below, the bypass valve assembly includes one or moreguide portions or grooves adapted to receive the inlet portion of theouter sheet metal shell for joining the outer sheet metal shell to thebypass valve assembly in a manner that hermetically seals the outersheet metal shell to the bypass valve assembly. In this regard, afeature of the bypass valve assembly encloses or otherwise circumscribesthe end of the inlet portion of the outer sheet metal shell. The inletportion of the inner sheet metal shell extends into the bypass valveassembly further than the end of the inlet portion of the outer sheetmetal shell to minimize leakage but remains spaced apart from the bypassvalve assembly by an air gap so that the inner sheet metal shell isfloating or freestanding with respect to the bypass valve assembly. Inother words, the inner sheet metal shell does not contact the bypassvalve assembly and is spaced a distance apart from the bypass valveassembly by the air gap. While a bypass valve of the bypass valveassembly may be operated to reduce or prevent exhaust gas flow throughthe turbine and thereby mitigate the impact of the thermal inertia ofthe turbine housing, in exemplary embodiments described herein, thebypass valve is closed at low engine revolutions per minute (RPMs) toboost intake air. Thus, reducing the thermal inertia of the exhaust gaspassageway decreases the amount of cooling of the exhaust gasattributable to the turbine housing, which in turn, helps to mitigateany potential impact of the turbine on downstream emissions controldevices during startup conditions.

FIG. 1 depicts an exemplary embodiment of a two-stage turbochargersystem 100 that includes a pair of turbocharger arrangements 110, 120,and may be designed for and utilized with any sort of vehicle, such as,for example, heavy-duty or performance automotive vehicles to light-dutyautomotive vehicles. A first turbocharger arrangement 110 includes afirst compressor 112 having an inlet arranged to receive ambient airdownstream of an air filter 102 for compression to provide charge airfor the cylinders of the vehicle engine 106. The first turbine 114 iscoaxially and concentrically aligned with the first compressor 112 andincludes a turbine wheel mounted or otherwise coupled to the compressorwheel (or impeller) of the low pressure compressor 112 via a commonrotary shaft 115. The first turbocharger arrangement 110 also includes abypass arrangement 116 operable to selectively bypass the first turbine114 and allow at least a portion of the exhaust gas to flow through abypass valve associated with the bypass arrangement 116 to a downstreamemissions arrangement 108 via ducting or another conduit withoutentering a volute for the turbine wheel. As described in greater detailbelow, in exemplary embodiments, the bypass arrangement 116 is realizedas a cast metal structure that is joined or otherwise mounted to thehousing of the turbine 114.

The second turbocharger arrangement 120 includes a second compressor 122having an inlet arranged to receive charge air downstream of the firstcompressor 112 for further compression (e.g., supercharging) subject tooperation of a bypass arrangement 128. In this regard, when the bypassarrangement 128 is open to bypass the second compressor 122, charge airfrom the first compressor 112 flows from the outlet of the firstcompressor 112 and through ducting or another conduit to an inlet of acharge air cooler 104 before provision to the engine intake or inletmanifold without entering a volute for the compressor wheel or withoutotherwise impacting the second compressor wheel. The second turbine 124is coaxially and concentrically aligned with the second compressor 122and includes a turbine wheel mounted or otherwise coupled to thecompressor wheel of the compressor 122 via a common rotary shaft 125.The second turbocharger arrangement 120 also includes a bypassarrangement 126 operable to selectively bypass the second turbine 124and allow at least a portion of the exhaust gas from the enginecylinders 106 to flow from the exhaust manifold(s) through a bypassvalve associated with the bypass arrangement 126 to an inlet of thefirst turbine 114 via ducting or another conduit without entering avolute for the turbine wheel or otherwise impacting the turbine wheel.

By virtue of the so-called “series” configuration of the turbines 114,124, the pressure of the input exhaust gases at the second turbine inletis greater than the pressure of the exhaust gases at the first turbineinlet, and accordingly, the second turbine 124 may alternatively bereferred to herein as the high-pressure (HP) turbine while the firstturbine 114 may alternatively be referred to herein as the low-pressure(LP) turbine. Similarly, by virtue of the so-called “series”configuration of the compressors 112, 112, the pressure of the inputexhaust gases at the second compressor inlet is greater than thepressure of the exhaust gases at the first turbine inlet, andaccordingly, the second compressor 122 may alternatively be referred toherein as the high-pressure (HP) compressor while the first compressor112 may alternatively be referred to herein as the low-pressure (LP)compressor.

In exemplary embodiments, the emissions arrangement 108 includes acatalytic converter or similar emissions control device having anefficacy that is influenced by the temperature of the exhaust gas at itsinlet. Accordingly, it is desirable to minimize the thermal inertiaassociated with the turbocharger system 100 downstream of the exhaustmanifold(s) of the engine 106 to facilitate a higher exhaust gastemperature at the inlet of the emissions arrangement 108. In theconfiguration depicted in FIG. 1, during startup conditions or atrevolutions per minute (RPM) below a transition threshold, thelow-pressure turbine bypass arrangement 116 is closed to achieve exhaustgas flow through the LP turbine 114 and corresponding operation of theLP compressor 112 to provide charge air to the engine 106. Thetransition threshold may be chosen as an RPM at which the likelihood ofthe LP turbine 114 becoming saturated or choked is greater than a LPturbine threshold percentage. Similarly, the HP bypass arrangements 126,128 may also be closed to achieve exhaust gas flow through the HPturbocharger arrangement 120 until reaching a second transitionthreshold at which the likelihood of the HP turbine 124 becomingsaturated or choked is greater than a HP turbine threshold percentage.

In exemplary embodiments, the HP turbine bypass arrangement 126 beginsbeing regulated or opened at an initial transition threshold that isless than that of the LP turbine bypass arrangement 116 (e.g., 1500 RPMversus 4500 RPM), so that exhaust gas flow through the LP turbine 114 ismore consistent and greater than that through the HP turbine 124 duringoperation of the turbocharger system 100. Thus, reducing the thermalinertia associated with the LP turbine 114 has a greater impact on theeffectiveness of the emissions arrangement 108. Accordingly, asdescribed in greater detail below, in exemplary embodiments describedherein, the LP turbine 114 includes a multilayer sheet metal housingthat defines at least a portion of the exhaust gas passageway throughthe LP turbine 114, and thereby reduces thermal inertia of the LPturbine 114.

FIGS. 2-9 depict an exemplary embodiment of a turbine housing assembly200 suitable for use in the turbocharger system 100 of FIG. 1, and inparticular, with the LP turbine 114. In this regard, FIG. 6 depicts theturbine housing assembly 200 when a rotating assembly 650 including aturbine wheel 610 (e.g., turbine wheel) and a corresponding compressorwheel 652 (e.g., compressor wheel) is inserted into the turbine housingassembly 200 and joined or mounted with a flange 240.

With initial reference to FIGS. 2-7, the turbine housing assembly 200includes a turbine housing defined by an inner sheet metal shell 202,204, an outer sheet metal shell 206, 208, and a central core structure220. The inner sheet metal shell 202, 204 includes a first sheet metalstructure 202 that faces a second sheet metal structure 204 in an axialdirection (the x reference direction) aligned with (or parallel to) therotational axis 600 of the turbine wheel 610 such that the sheet metalstructures 202, 204 interface and are joined in a radial plane that isaligned with (or parallel to) the plane in which the turbine wheel 610rotates (the yz reference plane). For purposes of explanation, the innersheet metal structure 202 closest to the turbine wheel 610 mayalternatively be referred to herein as the proximal inner sheet metalstructure and the inner sheet metal structure 204 farthest from theturbine wheel 610 may alternatively be referred to herein as the distalinner sheet metal structure. The outer sheet metal shell 206, 208includes a first outer sheet metal structure 206 that faces a secondouter sheet metal structure 208 in a direction substantiallyperpendicular to the rotational axis 600 of the turbine wheel 610 (e.g.,in the z reference direction) such that the outer sheet metal structures206, 208 interface and are joined in an axial plane that is aligned with(or parallel to) the rotational axis 600 of the turbine wheel 610 (thexy reference plane) and orthogonal to the plane in which the inner sheetmetal structures 202, 204 are joined.

With reference to FIGS. 4-7, the inner sheet metal structures 202, 204are formed to include respective base portions 203, 205 thatcooperatively define a radial inlet 700 tangential to a volute 212. Thevolute 212 is a voided region providing a scroll-shaped exhaust gaspassageway, and the volute 212 is defined by substantially circularportions 213, 215 that are integral with the base portions 203, 205 inconcert with a core structure 220. In this regard, the interior surfaces601, 603 of the base portions 203, 205 are contoured and configured inconcert with a tongue 218 to direct exhaust gas tangentially into thevolute 212 at the inlet 700 to the volute 212. The interior surfaces402, 602 of the volute portions 213, 215 are contoured to define theouter contour of the scroll-shaped voided region of the volute 212 thatnarrows moving radially from the inlet 700 to the opposing end of thetongue 218 that separates the volute 212 from the inlet 700.

As best illustrated in FIGS. 5-6, each of the inner sheet metalstructures 202, 204 includes a flange or similar feature 214, 216 thatextends radially outward from the volute portions 213, 215 to provide anarea for coupling the inner sheet metal structures 202, 204circumferentially about the volute portions 213, 215. In the illustratedembodiment, the flange 216 of the proximal inner sheet metal structure204 extends radially outward by a distance that is greater than or equalto the distance by which the flange 214 of the distal inner sheet metalstructure 202 extends to facilitate welding the flange 214 of the distalinner sheet metal structure 202 to the flange 216 of the proximal innersheet metal structure 204 substantially circumferentially about thevolute portions 213, 215. In one example, the proximal inner sheet metalstructure 204 and the distal inner sheet metal structure 202 are eachcomposed of a ferritic stainless steel material (e.g., SUS430J1L) andare coupled together via by tungsten inert gas (TIG) welding.

As best illustrated in FIG. 5, each of the substantially circular voluteportions 213, 215 of the inner sheet metal structures 202, 204 definesan interior opening 217, 219 that is substantially circular andcoaxially and concentrically aligned with the rotational axis 600 of theturbine wheel 610 to receive a central core structure 220. The centralcore 220 includes an interior voided region 222 (or hole or bore)coaxially and concentrically aligned with the rotational axis 600 of theturbine wheel 610 that includes a substantially circular or counterboreportion 224 for receiving and engaging a nose 611 of the turbine wheel610. The interior voided region 222 also includes a contoured portion226 having a circumference that increases moving away from the turbine610 along the axial direction (the x direction) aligned with therotational axis of the turbine 610 to define an axial outlet for theturbine 610. Stated another way, a diameter of the contoured portion 226varies along a length of the contoured portion 226, such that thediameter of the contoured portion 226 at a first end is different thanthe diameter of the contoured portion 226 at a second end. The distalend (or outlet end) of the core 220 includes a lip or similar feature656 that receives an outlet pipe 256, as described in greater detailbelow.

Referring to FIGS. 4 and 6-7, the central core 220 includes a tongueportion 218 that defines or otherwise separates the volute 212 from thetangential inlet thereto. As best illustrated in FIGS. 4 and 7, thecentral core 220 also includes a substantially continuous contouredouter surface 228 that faces the contoured inner surfaces 402, 602 ofthe volute portions 215, 217 of the inner sheet metal structures 202,204 to define the inner contour of the voided region providing thescroll-shaped exhaust gas passageway for the volute 212. In exemplaryembodiments, the central core structure 220 is realized as a unitarycast metal structure that is welded or otherwise affixed to the distalinner sheet metal structure 202, for example, by TIG welding about theopening 217 in the distal sheet metal structure 202, as described ingreater detail below. In one example, the central core structure 220 iscomposed of cast ferritic stainless steel material (e.g., SUS430).

With reference to FIG. 2-6, the outer sheet metal structures 206, 208are formed to include respective base portions 223, 225 thatcooperatively surround the inlet portions 203, 205 of the inner sheetmetal structures 202, 204 in a plane (the xz reference plane) that istransverse or orthogonal to the radial plane (the yz reference plane) inwhich the turbine wheel 610 rotates. The outer sheet metal structures206, 208 also include arcuate portions 227, 229 that cooperativelyenclose or surround the volute portions 213, 215 of the inner sheetmetal structures 202, 204 radially (e.g., in the yz reference plane). Asbest illustrated in FIGS. 2-3, in exemplary embodiments, one of theouter sheet metal structures 206 includes a receiving feature 280 formedtherein which is configured to overlap and mate with the other of theouter sheet metal structures 208 about the interface between the outersheet metal structures 206, 208 to facilitate joining the outer sheetmetal structures 206, 208 to one another. In one example, the outersheet metal structures 206, 208 are each composed of a ferriticstainless steel material (e.g., SUS409L) and are coupled together via byTIG welding. In this regard, the inner sheet metal shell 202, 204 andthe outer sheet metal shell 206, 208 may be realized using differentferritic stainless steel materials.

Additionally, the outer sheet metal structures 206, 208 includecontoured outlet portions 282, 284 that narrow moving away from theturbine wheel 610 in the axial direction (the x reference direction) tosubstantially enclose the inner sheet metal structures 202, 204 in theaxial direction (the x reference direction) opposite the turbine wheel610. As illustrated, the extension of the outer shell 206, 208 in thedirection parallel to the turbine wheel rotational axis 600 away fromthe turbine wheel 610 defined by the contoured outlet portions 282, 284is greater than the extension of the inner shell 202, 204 away from theturbine wheel 610 in the direction parallel to the turbine wheelrotational axis 600. At the same time, the extension of the inner shell202, 204 substantially perpendicular to the turbine wheel rotationalaxis 600 as defined by the inner base portions 203, 205 is greater thanthe extension of the outer shell 206, 208 substantially perpendicular tothe turbine wheel rotational axis 600 as defined by the outer baseportions 223, 225.

The contoured outlet portions 282, 284 define a substantially circularinterior opening 230 that is coaxially and concentrically aligned withthe rotational axis of the turbine wheel 610, with the opening 230 alsohaving a diameter that is less than the diameter of the circularinterior openings 217, 219 defined by the inner sheet metal structures202, 204. That said, it should be noted that depending on theembodiment, the axial outlet opening 230 defined by the outer sheetmetal structures 206, 208 may be off-axis or angled relative to therotational axis of the turbine 610, for example, due to packagingconstraints or the like. The ends 241, 243 of the outer sheet metalstructures 206, 208 defining the axial outlet opening 230 are coupled toa substantially-planar flange 238 via an outlet pipe 256 and collar 258for coupling the turbine housing assembly 200 to a fluid conduit forcarrying exhaust gas axially exiting the turbine wheel 610 to downstreamemissions devices (e.g., a catalytic converter 108), as described ingreater detail below.

Opposite the contoured outlet portions 282, 284 defining the axialoutlet opening 230, each of the outer sheet metal structures 206, 208includes a lip or similar receiving feature 607 defining at least aportion of a substantially circular opening 608 configured to receive asubstantially circular flange 240 for mounting the turbine housingassembly 200 to the rotating assembly 650. The rotating assemblygenerally includes the turbine wheel 610 and the compressor wheel 652coupled to the turbine wheel 610 via a common rotary shaft 654. As bestillustrated in FIG. 6, in exemplary embodiments, the inner circumferenceof the opening 608 defined by the axial ends 245, 247 of the outer sheetmetal structures 206, 208 proximal to the turbine 610 (or distal to theaxial outlet) is greater than or equal to an outer circumference of theflange 240 such that a portion of the flange 240 is received within theopening 608. Thus, the outer sheet metal shell 206, 208 defines abearing opening 608 having a radial dimension that is greater than thatof the volute 212 while also defining an opposing outlet opening 230having a radial dimension that is less than that of the bearing opening608 and the volute 212. Generally, the bearing flange 240 includes aplurality of bores 404 distributed about a perimeter or circumference ofthe flange 240, which each receive a respective fastener 640. Thefasteners 640 engage with the bores 404 to mount, support, or otherwisecouple the flange 240, and thereby the turbine housing assembly 200, tothe rotating assembly 650. It should be understood, however, that theflange 240 may be coupled to the rotating assembly 650 via anytechnique, such as an interference fit, welding, etc.

Still referring to FIGS. 2-6, the ends 233, 235 of the base portions223, 225 of the outer sheet metal structures 206, 208 are joined orotherwise coupled to a bypass valve assembly structure 232 that includesan opening 270 for a valve (e.g., bypass arrangement 116) that isoperable to allow exhaust gas to selectively bypass the tangential inletto the volute 212, and thereby bypass the turbine 610. In this regard,the bypass opening 270 extends along an axis that is oblique to the axisof the inlet opening 632, as illustrated in FIGS. 4, 6 and 8. Inexemplary embodiments, the bypass valve assembly structure 232 isrealized as a unitary cast metal material that includes a flange 231 (orlip) that receives and circumscribes the ends 233, 235 of the baseportions 223, 225 of the outer sheet metal structures 206, 208 in theaxial plane (the xz reference plane) transverse to the radial plane (theyz reference plane) in which the turbine wheel 610 rotates.

As best illustrated in FIGS. 6 and 8, the bypass valve assemblystructure 232 also includes a corresponding guide portion 234 having anouter circumference that is less than or equal to an inner circumferenceof the lip feature 231 and an inner circumference that is less than orequal to an inner circumference of the ends 233, 235 of the combinedouter sheet metal base 223, 225 for receiving and supporting the ends233, 235 of the outer sheet metal base portions 223, 225. In thisregard, the guide portion 234 may be realized as a shelf or surfaceabout the perimeter of an inlet opening 632 in the bypass valve assemblystructure 232 that includes one or more features 802, 804, 806, 808 thatengage the ends 233, 235 of the outer sheet metal base portions 223,225. The features 802, 804, 806, 808 may have distinct or differentshapes and be spaced apart about the perimeter of the guide portion 234,and the features 802, 804, 806, 808 may be configured to mate withcorresponding features on the base portions 223, 225 of the outer sheetmetal structures 206, 208 when the outer sheet metal structures 206, 208are inserted into the bypass valve assembly structure 232. Theoverlapping portion of the lip 231 is subsequently welded to the outersurfaces of the outer sheet metal base portions 223, 225 about itsperimeter to hermetically seal the outer sheet metal structures 206, 208to the bypass valve assembly structure 232.

Referring to FIG. 6, the bypass valve assembly structure 232 furtherincludes an accommodation portion 236. The accommodation portion 236 maycomprise a countersink defined in the inlet opening 632 of the bypassvalve assembly structure 232. The accommodation portion 236 generallyhas an outer circumference that is less than or equal to an innercircumference of the ends 233, 235 of the combined outer sheet metalbase 223, 225. The accommodation portion 236 is further recessed intothe bypass valve assembly structure 232 relative to the guide portion234 to accommodate extension of the inner sheet metal base portions 203,205 into the bypass valve assembly structure 232 without contacting thebypass valve assembly structure 232. In this regard, the ends 237, 239of the base portions 203, 205 of the inner sheet metal structures 202,204 extend into the bypass valve assembly structure 232 (in the −yreference direction) by a distance (d₁) relative to the end of the lipfeature 231 that is greater than the distance (d₂) that the outer sheetmetal base ends 233, 235 extend beyond the end of the lip feature 231into the bypass valve assembly structure 232 to minimize leakage betweenthe inner and outer sheet metal shells. At the same time, an air gap orseparation distance 630 is maintained between the ends 237, 239 of theinner sheet metal base portions 203, 205 and the accommodation portion236 of the bypass valve assembly structure 232 so that the inner sheetmetal base portions 203, 205 do not contact the bypass valve assemblystructure 232 and are freestanding with respect to the bypass valveassembly structure 232.

As best illustrated in FIGS. 5-7, in exemplary embodiments, an energyabsorbing member 260, 262 is provided on an interior surface of each ofthe outer sheet metal structures 206, 208. In one example, the energyabsorbing members 260, 262 are disposed between the respective outersheet metal structure 206, 208 and the inner sheet metal structures 202,204. In this example, the energy absorbing members 260, 262 are arcuatesheet metal structures that substantially conform to the interiorsurface of the respective outer sheet metal structure 206, 208 and arewelded (e.g., spot welding) to the interior surface of the respectiveouter sheet metal structure 206, 208 at locations that overlap portionsof the outer sheet metal structures 206, 208. In this regard, by virtueof the shape of the outer sheet metal structures 206, 208, the upperportions of the outer sheet metal structures 206, 208 distal to the baseportions 223, 225 where the outer sheet metal structures 206, 208interface may be more susceptible to wheel burst. Accordingly, theenergy absorbing members 260, 262 may be strategically placed toradially surround at least a portion of the volute 212 defined by theinner sheet metal structures 202, 204 adjacent to the location where theouter sheet metal structures 206, 208 are joined to provide additionalradial containment.

In exemplary embodiments, the axial dimension (or width) of the energyabsorbing members 260, 262 parallel to the turbine rotational axis 600is configured to radially overlap portions the volute 212 forcontainment purposes, but without extending beyond the volute 212 in theaxial direction to minimize the amount of material and weightcontributed to the turbine housing assembly 200 by the energy absorbingmembers 260, 262. In this regard, the energy absorbing members 260, 262and the volute 212 may be coplanar with the edges or ends of the energyabsorbing members 260, 262 that are distal to the turbine 610 beingsubstantially aligned with the distal extent of the volute 212 in theradial plane, as best illustrated in FIGS. 5-6. At the same time, theradial dimension (or length) of the energy absorbing members 260, 262 isalso chosen to minimize the amount of material and weight contributed tothe turbine housing assembly 200 by the energy absorbing members 260,262 while strategically providing radial containment at the desiredlocations.

In one or more exemplary embodiments, the thickness of the outer sheetmetal structures 206, 208 is greater than the thickness of the innersheet metal structures 202, 204, that is, the outer sheet metalstructures 206, 208 may be formed from a metal sheet having a thicknessthat is greater than the metal sheet used to form the inner sheet metalstructures 202, 204. In this regard, the metal sheet used to form theinner sheet metal structures 202, 204 may be made as thin as practicablefor thermal performance, with a thicker metal sheet being used for theouter sheet metal structures 206, 208 to obtain a resulting combinedthickness that achieves the desired containment and reliability. Forexample, in one embodiment, the wall thickness of the volute portions213, 215 of the inner sheet metal structures 202, 204 is approximately1.2 millimeters (mm) and the wall thickness of the arcuate portions 227,229 of the outer sheet metal structures 206, 208 is approximately 3 mmto provide a total thickness of about 4.2 mm, which corresponds to thewall thickness of a corresponding cast component of similar dimensions.

In one or more embodiments, the thickness of the energy absorbingmembers 260, 262 is chosen to achieve the casting thickness at thelocations of the outer sheet metal structures 206, 208 most susceptibleto loss of containment. For example, if the cast component thickness is4.5 mm, and the inner sheet metal structures 202, 204 have a wallthickness of approximately 1.2 mm and the outer sheet metal structures206, 208 have a wall thickness of approximately 3 mm, the thickness ofthe energy absorbing members 260, 262 may be chosen to be approximately0.3 mm to achieve a combined thickness of 4.5 mm. In yet anotherembodiment, the same type of sheet metal is used for the outer sheetmetal structures 206, 208 and the energy absorbing members 260, 262, andthe thicknesses of the outer sheet metal structures 206, 208 and theenergy absorbing members 260, 262 substantially identical and chosen toprovide the cast component thickness. For example, if the cast componentthickness is 4.5 mm and the inner sheet metal structures 202, 204 have awall thickness of 1.3 mm, then both the outer sheet metal structures206, 208 and the energy absorbing members 260, 262 may have a thicknessof approximately 1.6 mm to achieve a combined thickness of 4.5 mm Thus,the thickness of the outer sheet metal structures 206, 208 and theenergy absorbing members 260, 262 may be dictated by the thickness ofthe inner sheet metal structures 202, 204 and the required amount ofcontainment, which, in turn, allows for the thickness of the inner sheetmetal structures 202, 204 to be optimized to achieve the desiredperformance qualities.

Still referring to FIGS. 2-8, to fabricate the turbine housing assembly200, the core structure 220 is inserted into the opening 217 of thedistal inner sheet metal structure 202, and the distal inner sheet metalstructure 202 is joined to the core structure 220 by tungsten inert gas(TIG) welding circumferentially about the opening 217 to an outersurface of the core structure 220 facing the axial outlet opposite theturbine wheel 610 to hermetically seal the distal sheet metal structure202 to the core structure 220. The ends of the proximal inner sheetmetal structure 204 that define the opening 219 for receiving theturbine wheel 610 are inserted into a corresponding opening defined bythe flange 240 and joined circumferentially about the opening 219 by TIGwelding to hermetically seal the sheet metal structure 204 to the flange240. Thereafter, the inwardly facing ends of the inner sheet metalstructures 202, 204 are joined to one another by TIG welding about theinterface between the inner sheet metal structures 202, 204 in theradial plane to hermetically seal the inner sheet metal structures 202,204 to one another in the axial direction. Thus, the volute portions213, 215 are substantially circumferentially welded to one another atthe portions where the rims 214, 216 meet to provide a hermeticallysealed radial outer contour for the volute 212. The resulting weldingseam or joint about the inner sheet metal structures 202, 204 resides ina radial plane (e.g., the yz reference plane) that is substantiallyparallel to the plane in which the turbine wheel 610 rotates andsubstantially perpendicular to the turbine wheel rotational axis 600.

As illustrated by the detailed view of region 900 in FIG. 9, inexemplary embodiments, the core structure 220 is not welded or joined tothe proximal inner sheet metal structure 204, so that the core structure220 is freestanding with respect to the proximal inner sheet metalstructure 204. In particular, at ambient temperatures, the tongueportion 218 of the core structure 220 proximate the inlet is spacedapart from a corresponding tongue feature in the proximal inner sheetmetal structure 204 separating the interior portion of the volute 212from the inlet by an air gap 902 having a nonzero separation distance toaccommodate thermal expansion of the inner sheet metal structure 204,and thereby reduce stress on the tongue portion 218 of the corestructure 220. In this regard, the air gap 902 may be chosen to providea separation distance at ambient temperatures that results in at leastsome separation distance being maintained at elevated exhaust gastemperatures during operation. In some embodiments, the inner sheetmetal structure 204 may contact the tongue portion 218 of the corestructure 220 during operation but only do so at or near its maximalthermal expansion, so that any stress imparted on the core structure 220is minimized. For example, in one embodiment, the air gap 902 orseparation distance between the tongue portion 218 and the correspondingtongue feature in the proximal inner sheet metal structure 204 is about0.5 millimeters at ambient temperatures so that at a maximum operatingtemperature of 850° Celsius, the tongue portion 218 and thecorresponding tongue feature in the proximal inner sheet metal structure204 contact one another without causing any significant stress on eitherof the core structure 220 or the sheet metal structure 204.

After assembling the inner sheet metal structures 202, 204 with the corestructure 220 and bearing flange 240, an axial outlet pipe 256 isinserted into a corresponding guide feature formed in the inner surfaceof the distal end of the outlet portion 226 of the core structure 220and joined to the inner surface of the outlet portion 226 about theproximal end of the outlet pipe 256 by TIG welding, thereby hermeticallysealing the axial outlet pipe 256 to the core structure 220. An outletcollar 258 is provided over the distal end of the outlet pipe 256.

Still referring to FIGS. 2-6, the energy absorbing members 260, 262 arejoined to the inner surfaces of the respective outer sheet metalstructures 206, 208 by spot welding. Thereafter, the upper portions ofouter sheet metal structures 206, 208 opposite the base portions 223,225 are joined about the assembled inner sheet metal structures 202, 204by TIG welding the overlapping portions of the outer sheet metalstructures 206, 208 together in the xy reference plane to radiallyenclose the volute portions 213, 215 in the yz reference plane. In thisregard, a welding seam extends along the radius (or diameter) of thearcuate portions 227, 229 from the outlet ends 241, 243 of the outersheet metal structures 206, 208 along the overlapping interface betweenthe sheet metal structures 206, 208 (e.g., where the receiving feature280 of structure 206 overlaps the end 243 of structure 208). Theresulting welding seam or joint between the outer sheet metal structures206, 208 resides in an axial plane that is substantially parallel to theturbine wheel rotational axis 600 and substantially perpendicular ortransverse to the plane in which the turbine wheel 610 rotates, as bestillustrated by FIGS. 2-3. In this regard, the plane the welding seambetween the outer sheet metal structures 206, 208 resides in issubstantially perpendicular or otherwise transverse to the radial planein which the welding seam between the inner sheet metal structures 202,204 resides, and the portion of the welding seam between arcuateportions 227, 229 opposite the inlet opening 632 and radiallysurrounding the volute 212 extends in an axial direction substantiallyparallel to a turbine wheel rotational axis 600.

Additionally, the distal ends 241, 243 of the outer sheet metalstructures 206, 208 defining the axial outlet opening 230 are weldedcircumferentially about the outlet collar 258, which, in turn, supportsthe distal end of the outlet pipe 256 extending from the core structure220 in the radial plane (the yz reference plane). In exemplaryembodiments, the welding of the outlet pipe 256 to the outlet ends 241,243 of the outer sheet metal structures 206, 208 and the welding of theupper portions of outer sheet metal structures 206, 208 are performedduring the same welding process step.

The ends 233, 235 of the base portions 223, 225 are inserted into theguide portion 234 of the cast bypass valve structure 232. The baseportions 223, 225 of the outer sheet metal structures 206, 208 are thenjoined in the xy reference plane by TIG welding the interface betweenthe outer sheet metal structures 206, 208 from the outlet pipe 256 tothe interface with the bypass valve assembly structure 232. Theperimeter of the lip 231 of the guide portion 234 is also welded to theoverlapped outer surfaces of the outer sheet metal structures 206, 208in a plane substantially parallel to the turbine wheel rotational axis600 (e.g., the xz reference plane) to hermetically seal the outer sheetmetal structures 206, 208 to the bypass valve structure 232. Thus, theouter sheet metal structures 206, 208 and the bypass valve structure 232cooperatively enclose the inner sheet metal structures 202, 204radially, with the outer sheet metal structures 206, 208 and the bearingflange 240 enclosing the inner sheet metal structures 202, 204 axially.In exemplary embodiments, the welding of the lower portions of the outersheet metal structures 206, 208 and the welding of the outer sheet metalbase portions 223, 225 with the bypass valve assembly structure 232 areperformed during the same welding process step. It should be noted thatby virtue of the axial interface between the outer sheet metalstructures 206, 208, the distance or amount of welding required to jointhe outer sheet metal structures 206, 208 is reduced as compared towelding circumferentially in a radial plane (e.g., a radial or diametricwelding seam as compared to a circumferential welding seam).

As described above, the inlet ends of the base portions 237, 239 of theinner sheet metal structures 202, 204 extend further into the bypassvalve structure 232 than the ends 233, 235 of the outer sheet metal baseportions 223, 225 (e.g., into the recessed portion 236) to minimize anyleakage at the inlet via the air gap between the ends of the inner baseportions 237, 239 and the bypass valve structure 232 and into any gapsor spaces between the inner sheet metal structures 202, 204 and theouter sheet metal structures 206, 208. The separation distance betweenthe inner base portions 237, 239 and the bypass valve structure 232accommodates thermal expansion of the inner sheet metal structures 202,204 resulting from the exhaust gas flow.

The outlet collar 258 is inserted into a corresponding opening in theexhaust outlet flange 238 and is circumferentially welded to the innersurface of the opening in the flange 238 to hermetically seal theexhaust gas passageway. In some embodiments, the axial outlet ends ofthe outlet pipe 256 and the outlet collar 258 are both weldedcircumferentially to the inner surface of the opening in the flange 238concurrently to effectively weld all three structures 238, 256, 258together and seal the outlet end of the exhaust gas passageway. Inexemplary embodiments, the exhaust outlet flange 238 is formed from orotherwise realized using sheet metal. As illustrated in FIG. 2, in someembodiments, the outlet ends of the outer sheet metal structures 206,208 defining the axial outlet opening 230 that receives the outlet pipe256 and collar 258 may be spaced apart or otherwise offset from theoutlet flange 238. Thus, the outlet pipe 256 and collar 258 mayaccommodate variations in the position or orientation of the flange 238with respect to the outer sheet metal structures 206, 208 duringmanufacturing or assembly. That said, by virtue of circumferentiallywelding the outlet ends of the outer sheet metal structures 206, 208 tothe collar 258, which, in turn is welded to the outlet pipe 256 and theoutlet flange 238, the axial outlet exhaust gas passageway ishermetically sealed from the core structure 220 to the ductingdownstream of the flange 238. In this regard, the outlet pipe 256 andcollar 258 provide a hermetically sealed passageway when the axialoutlet portion 226 of the core 220 is not welded or sealed to the outersheet metal structures 206, 208.

After the turbine housing assembly 200 is fabricated, the turbine noseportion 211 of the assembly 250 is inserted into the correspondingportion 224 of the core structure 220, with the assembly 250 beingmounted or otherwise joined to the turbine housing assembly 200 usingthe flange 240 in a manner that hermetically seals the flange 240 to theassembly 250. In exemplary embodiments, the turbine nose portion 211includes one or more sealing rings circumscribing the outer surface ofthe turbine nose portion 211 to hermetically seal the axial outlet fromthe turbine wheel 610 with the opening 222 for the axial outlet providedwithin the core structure 220. Variable geometry members (e.g., guidevanes or the like) may be provided within the assembly 250 about theturbine wheel 610 and configured to regulate, control, or otherwiseinfluence the exhaust gas flow from the volute 212 to the turbine wheel610, as will be appreciated in the art.

By virtue of the inner sheet metal structures 202, 204 defining at leastthe outer contour of the volute 212 and the inlet thereto, thepercentage of surface area encountered by the exhaust gas that is sheetmetal is increased, which, in turn reduces the reduction in exhaust gastemperature at the opening in the exhaust outlet flange 238 relative tothe exhaust gas temperature upon entry to the bypass valve structure232. Additionally, the inner sheet metal structures 202, 204 arerelatively thin, to further reduce the thermal inertia associated withthe exhaust gas flow through the volute 212. Thus, the effectiveness ofdownstream emissions devices may be improved. The relatively thickerouter sheet metal structures 206, 208 provide containment for the volute212 while also being constructed from sheet metal to reduce thermalinertia. At the same time, the bypass valve structure 232 is realized asa cast metal to support the remaining components of the turbine housingassembly 200 subject to any external loading caused by the ductingjoined to the valved opening 270, ducting joined to the exhaust outletflange 238, or the assembly 250 joined to the turbine housing assembly200. The cast bypass valve structure 232 also helps maintain the opening270 (e.g., by avoiding closure due to thermal expansion or deformation)and support robust and reliable operation of the bypass valve components(e.g., the valve, the arm or actuation element for the valve, and thebushings or other components that facilitate actuation) across a rangeof variable temperature and mass flow conditions and subject topotentially varying amounts of external loading. Additionally, the corestructure 220 is realized as a cast metal to similarly provide robustand reliable operation across a range of variable temperature and massflow conditions, namely, by providing a tongue portion 218 and othersurfaces of the volute 212 that are less susceptible to deformation,thermal expansion, or the like. That said, by virtue of the voluteportions 213, 215 and base inlet portions 203, 205 provided by the innersheet metal structures 202, 204, the exposed surface area within thevolute 212 and the inlet thereto that is realized as a cast metal may bereduced or otherwise minimized to achieve a corresponding reduction inthe thermal inertia associated with the turbine housing assembly 200.

By virtue of the flanges 214, 216 about the radial interface between theinner sheet metal structures 202, 204, the area for the welding seamjoining the inner sheet metal structures 202, 204 may be increased tofacilitate a more consistent and stable weld about the circumferentialinterface of the volute portions 213, 215, and thereby may improvewelding quality. Improved weld quality in concert with the radial seamorientation may result in improved stiffness for purposes of improvedcontainment and may also help minimize volute deformation. Additionally,the welding seam direction for the weld joining the outer sheet metalstructures 206, 208 minimizes the welding length (radially ordiametrically versus circumferentially), which is advantageous forcontainment capability, which is further augmented by the increasedthickness of the outer sheet metal structures 206, 208. The additionalenergy absorbing members 260, 262 radially overlapping the volute 212further improve containment, with placement of the energy absorbingmembers 260, 262 proximate the joint between the outer sheet metalstructures 206, 208 reinforcing relatively flatter sections of the outersheet metal structures 206, 208 radially circumscribing the volute 212.At the same time, the axial and radial dimensions of the energyabsorbing members 260, 262 may be minimized so that they only radiallyoverlap the volute 212 at strategically advantageous locations to reducematerial costs and weight.

As described above in the context of FIG. 1, at startup, the valve inthe opening 270 is closed so that exhaust gas flows through the volute212 and impacts the turbine wheel 610 before exiting the axial outlet222, 230 to downstream emissions devices 108. By limiting the cast metalsurface area encountered by the exhaust gas to the tongue 218 andcontoured surface 228 of the core structure 220 and the outlet 222 ofthe core structure 220, the effective thermal inertia of the turbinehousing assembly 200 relative to a corresponding cast turbine housingassembly is reduced. As a result, the exhaust gas that reaches thedownstream emissions devices 108 has a higher temperature relative to acast turbine housing assembly, and as a result, the performance of thedownstream emissions device 108 is improved. At the same time, the sheetmetal may also be utilized to minimize the size, weight, form factor, orthe like associated with the turbine housing assembly 200 withoutcompromising burst containment by virtue of the configuration describedherein.

For the sake of brevity, conventional techniques related to turbines,compressors, turbochargers, wastegates, bypass valves, ducting,catalytic converters, emissions controls, and other functional aspectsof the systems (and the individual operating components of the systems)may not be described in detail herein. Furthermore, the various figurescontained herein are intended to represent exemplary functionalrelationships and/or physical couplings between the various elements. Itshould be noted that many alternative or additional functionalrelationships or physical connections may be present in an embodiment ofthe subject matter.

The foregoing description may refer to elements or components orfeatures being “coupled” together. As used herein, unless expresslystated otherwise, “coupled” means that one element/node/feature isdirectly or indirectly joined to (or directly or indirectly communicateswith) another element/node/feature, and not necessarily mechanically.Thus, although the drawings may depict one exemplary arrangement ofelements, additional intervening elements, devices, features, orcomponents may be present in an embodiment of the depicted subjectmatter. In addition, certain terminology may also be used in thefollowing description for the purpose of reference only, and thus arenot intended to be limiting. For example, the terms “first,” “second,”and other such numerical terms referring to structures do not imply asequence or order unless clearly indicated by the context. Similarly,terms such as “upper”, “lower”, “top”, and “bottom” refer to directionsin the drawings to which reference is made.

The foregoing detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any theory presentedin the preceding background, brief summary, or the detailed description.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of thesubject matter in any way. Rather, the foregoing detailed descriptionwill provide those skilled in the art with a convenient road map forimplementing an exemplary embodiment of the subject matter. It should beunderstood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope of the subject matter as set forth in theappended claims. Accordingly, details of the exemplary embodiments orother limitations described above should not be read into the claimsabsent a clear intention to the contrary.

What is claimed is:
 1. A turbine housing assembly comprising: an innershell comprising: an inner base portion defining an inlet; and a voluteportion defining an outer contour of a volute in fluid communicationwith the inlet; an outer shell circumscribing the volute portion in aradial plane and including an outer base portion circumscribing theinner base portion, wherein: the inner shell comprises a first pluralityof sheet metal structures joined to one another in the radial plane; theouter shell comprises a second plurality of sheet metal structures;first portions of the second plurality of sheet metal structuressurrounding the volute portion are joined to one another in an axialplane transverse to the radial plane; a first extension of the innerbase portion relative to a turbine wheel rotational axis is greater thana second extension of the outer base portion relative to the turbinewheel rotational axis; and a third extension of the outer shell alongthe turbine wheel rotational axis distal to a turbine wheel is greaterthan a fourth extension of the inner shell along the turbine wheelrotational axis distal to the turbine wheel.
 2. The turbine housingassembly of claim 1, wherein: the first plurality of sheet metalstructures are coupled about the volute portion; and second portions ofthe second plurality of sheet metal structures enclosing the voluteportion in an axial direction are coupled diametrically.
 3. The turbinehousing assembly of claim 1, wherein the outer shell defines a bearingopening having a radial dimension greater than a radial dimension of thevolute portion and an outlet opening in an axial direction opposite thebearing opening.
 4. The turbine housing assembly of claim 3, wherein theouter shell encloses the inner shell in the axial direction opposite thebearing opening.
 5. The turbine housing assembly of claim 1, wherein:each of the first plurality of sheet metal structures includes a flangeextending radially outward from the volute portion; and the flanges ofthe first plurality of sheet metal structures are welded together. 6.The turbine housing assembly of claim 1, wherein each of the secondplurality of sheet metal structures comprises an arcuate portionextending from a respective portion of the outer base portion.
 7. Theturbine housing assembly of claim 6, wherein an interface between thearcuate portions is welded in an axial direction substantially parallelto the turbine wheel rotational axis.
 8. The turbine housing assembly ofclaim 1, wherein a thickness of the outer shell is greater than athickness of the inner shell.
 9. The turbine housing assembly of claim1, wherein the inner shell and the outer shell are freestanding withrespect to one another.
 10. The turbine housing assembly of claim 1,wherein the first portions of the second plurality of sheet metalstructures overlap in an axial direction aligned with the turbine wheelrotational axis.
 11. A turbine housing assembly comprising: an innershell comprising a first plurality of sheet metal structures joined toone another at a first seam in a radial plane; and an outer shellcomprising a second plurality of sheet metal structures joined to oneanother at a second seam in an axial plane transverse to the radialplane, wherein: the inner shell includes a volute portion defining anouter contour of a volute in the radial plane; the outer shellsubstantially surrounds the volute portion and encloses the voluteportion in an axial direction; and an outer base portion of the outershell circumscribes an inner base portion of the inner shell thatdefines an inlet in fluid communication with the volute; a firstextension of the inner base portion relative to a turbine wheelrotational axis is greater than a second extension of the outer baseportion relative to the turbine wheel rotational axis; and a thirdextension of the outer shell along the turbine wheel rotational axisdistal to a turbine wheel is greater than a fourth extension of theinner shell along the turbine wheel rotational axis distal to theturbine wheel.
 12. The turbine housing assembly of claim 11, wherein athickness of the outer shell is greater than a thickness of the innershell.
 13. The turbine housing assembly of claim 11, wherein the voluteportion of the first plurality of sheet metal structures is welded aboutat least a portion of a perimeter to provide the first seam.
 14. Theturbine housing assembly of claim 13, wherein portions of the secondplurality of sheet metal structures are welded along at least a portionof a radius to provide the second seam.
 15. The turbine housing assemblyof claim 14, wherein the portions of the second plurality of sheet metalstructures enclose the volute portion in the axial direction.
 16. Theturbine housing assembly of claim 11, wherein: each of the firstplurality of sheet metal structures includes a flange extending radiallyoutward; and the flanges of the first plurality of sheet metalstructures are welded together about the volute portion.
 17. The turbinehousing assembly of claim 11, wherein the inner shell and the outershell are freestanding with respect to one another.
 18. A turbinehousing assembly comprising: an inner sheet metal shell comprising afirst pair of sheet metal structures coupled together along a radialplane orthogonal to a turbine wheel rotational axis; and an outer sheetmetal shell comprising a second pair of sheet metal structures coupledtogether along a first plane transverse to the radial plane, wherein:each of the first pair of sheet metal structures includes a voluteportion defining an outer contour of a volute in the radial plane and abase portion defining an inlet in fluid communication with the volute;each of the second pair of sheet metal structures includes an arcuateportion radially overlapping at least a portion of the volute portionsin the radial plane and an outer base portion radially overlapping atleast a portion of the base portions in a second plane transverse to theradial plane; a first extension of the base portion of the first pair ofsheet metal structures relative to a turbine wheel rotational axis isgreater than a second extension of the outer base portion of the secondpair of sheet metal structures relative to the turbine wheel rotationalaxis; and a third extension of the outer sheet metal shell along theturbine wheel rotational axis distal to a turbine wheel is greater thana fourth extension of the inner sheet metal shell along the turbinewheel rotational axis distal to the turbine wheel.
 19. The turbinehousing assembly of claim 18, wherein: each of the first pair of sheetmetal structures includes a flange extending radially outward about thevolute portion; the flanges of the first pair of sheet metal structuresare coupled together circumferentially about the volute portion;overlapping portions of the arcuate portions are coupled together in anaxial direction aligned with the turbine wheel rotational axis tosurround the volute portions; and each of the second pair of sheet metalstructures includes a tapered outlet portion coupled to the other toenclose the volute portion in the axial direction.